1. Field of the Invention
Embodiments of the present disclosure generally relate to power systems and, more particularly, to a method and apparatus for characterizing a circuit coupled to an AC line.
2. Description of the Related Art
Solar panels have historically been deployed in mostly remote applications, such as remote cabins in the wilderness or satellites, where commercial power was not available. Due to the high cost of installation, solar panels were not an economical choice for generating power unless no other power options were available. However, the worldwide growth of energy demand is leading to a durable increase in energy cost. In addition, it is now well established that the fossil energy reserves currently being used to generate electricity are rapidly being depleted. These growing impediments to conventional commercial power generation make solar panels a more attractive option to pursue.
Solar panels, or photovoltaic (PV) modules, convert energy from sunlight received into direct current (DC). The PV modules cannot store the electrical energy they produce, so the energy must either be dispersed to an energy storage system, such as a battery or pumped hydroelectricity storage, or dispersed by a load. One option to use the energy produced is to employ inverters to convert the DC current into an alternating current (AC) and couple the AC current to the commercial power grid. The power produced by such a distributed generation (DG) system can then be sold to the commercial power company.
In order to mitigate potential safety hazards, a DG coupled to a commercial power grid must be operated in accordance with relevant regulatory requirements, such as IEEE-1547. As part of meeting the IEEE-1547 requirements, an inverter within a DG must shut down under certain circumstances, including line frequency or line voltage operating outside of pre-defined limits. The IEEE-1547 standard specifies that such voltage requirements must be met at a Point of Common Coupling (PCC) between the commercial power system and the DG (i.e., a point of demarcation between the public utility service and the DG).
In cases where a DG is located some distance from the PCC, electrical power data acquisition equipment must be installed at the PCC to monitor the relevant electrical parameters. Installing the data acquisition equipment requires manually intensive work to ensure that voltage sense leads and current sensors of the acquisition equipment are connected to the appropriate leads and have the proper orientation. Additionally, identification of a circuit type as a load or a source and determination of circuit voltage characteristics (e.g., single phase, split phase) must be manually performed. Proper installation of the data acquisition equipment is critical to provide accurate monitoring of the electrical data; improperly connected data acquisition equipment could result in invalid data and therefore present a potential safety hazard.
Therefore, there is a need for a method and apparatus for automatically determining characteristics of a circuit coupled to an AC line.